This invention relates to a cryogenic envelope for a transmission line. In this respect, a preferred embodiment of the invention will be described in connection with a cryogenic envelope for a flexible superconducting power transmission line.
In order to be commercially attractive, superconductive power transmission lines must have low thermal losses and high reliability. Consequently, it is an object of this invention to provide a transmission line having a cryogenic envelope that is both reliable and results in a low heat-leak structure.
One problem with existing transmission lines is that they tend to buckle or break when either being warmed up for repairs or cooled down upon being placed into operation. Consequently, one of the embodiments about to be described includes structure for permitting various components of the envelope to suitably expand and contract during warm up or cooldown.
Also, for the long distances required for power-transmission lines, a problem is presented by the contraction and expansion of the refrigeration tubes. Hence, another illustrated embodiment describes a refrigeration tube that is expansible or contractible independently of the main envelope.